Colder Weather for February?

Hello everyone and welcome to another blog post! Firstly, I just want to say thank you for all the support and visits to the website recently! We had 264 visits in the first 5 days! Now that I have said that, I am now going to start with the blog, which is the potential for colder weather this February, and rumours of a Beast From the East (mainly from the Daily Express XD)

Over the past few days, we have been consistently teased by numerous models with runs like this, big blocking to the North of the UK, bringing in a bitterly cold Easterly wind, with some runs even bringing the -15c isotherm to SE parts. However, you cannot base a forecast just on a few model runs. You need to see what is driving the forecast. So, let's take a look at the bigger picture, and take a look at everyone's favourite - ensembles. 

Ensembles

You can see the clear scatter as we go to the end of the period, there is pretty much no agreement of any kind of weather whatsoever, so from this alone it's pretty inconclusive. So to put a little bit more onto this let's look at ENS meteograms. This one is for Reading

This is basically the same chart as before, put into a different format. But on this one the downward trend is a lot clearer, with a clear signal for colder weather from the ECMWF. By checking the geopotential height anomalies on the ECMWF ENS we can see a that it is supporting Northern Blocking. That is when high pressure sets up at Northern latitudes, and send the jetstream, and any low pressure with it, southwards.

That generally stops mild air from coming into the UK, and can often favour a period of cold weather. We can also see that the ensembles favour blocking, with a trend for increased heights over parts of Scandinavia on the ENS. 

MJO

The MJO is a measure of different phases of convection across Tropical areas of the world, and it tends to help see what kind of weather pattern you can expect. 

You can see that all the lines and shading are moving into the phase 6 and 7 areas, and these phases mean enhanced rainfall is now moving into the Western Pacific. This tends to favour a -NAO, as well as blocking, both of which favour colder weather in the UK.  

Stratosphere

The developments in the stratosphere I quite important in the outlook for colder weather. To favour colder weather, we typically want a reversal of the zonal winds high up in the atmosphere, as well as a warming. At the beginning of January, we saw a major SSW event, as well as a reversal of the zonal wind

We can see that the GFS is forecasting a rather significant weakening of the polar vortex, and this is also couple with some general warming at 10hPa (the stratosphere) over the next few days. So the stratosphere supports blocking and colder weather.

Summary

So most ways of looking at the forecast suggest blocking is favourable or even likely, so the crazy weather runs being pumped out by the weather models aren't too unrealistic then? Well... yes and no. Firstly, increased blocking does look likely, and this does increase the chance of cold weather, but still lots depends. Although there may be large areas of high pressure that are formed as a result of this, still lots needs to happen before cold weather happens. The high could end up in an amplification of the jet stream, bringing mild weather to the UK, or it could end up to the north, bringing cold, but not very cold weather, like it did at the beginning of January. It takes a lot to bring a Beast from the East, but the chances are definitely increasing...

Alex